Disposable plastic food-service items are in increasingly widespread use for storing, serving and consuming food, due to their reasonably low-cost and the convenience they provide. Disposable food containers and articles range from non-returnable containers such as yogurt cups and dinner entree packaging, to microwavable storage containers and general tableware items such as plastic plates, cups and cutlery. The increasing popularity of fast-food restaurant chains further fuels the demand for plastic tableware. In addition to the fast food restaurants, caterers also prefer disposable food service items for the associated convenience, hygiene and competitive-costs. In this regard it is important to note that replacement costs for disposable items such as cutlery are offset by the clean-up costs (labor, materials and equipment) associated with metal cutlery.
The presence of non-disposable metal cutlery along with other disposable food-service articles such as plates, cups and the like presents unusual problems for restaurants and caterers. The problems stem from the loss of valuable metal cutlery into trash or refuse containers along with disposable tableware and food remnants. The problem can be further accentuated during peak business hours where time-pressures can further cause leftover food on a plate together with one or more items of cutlery to be scrapped. Previous attempts to circumvent this problem are known. U.S. Pat. No. 4,632,253 describes apparatus for separating cutlery from restaurant waste, including a chute for the waste and an inductive type probe with associated evaluation logic for sending an electric switching signal when an item of cutlery passes along the chute.
Another problem that food caterers encounter is the ability to clean metal flatware utensils at certain locations and outdoor catering events. In preparation for such circumstances caterers tend to carry a large inventory of expensive metal cutlery. The use of disposable plastic cutlery for such catering events would eliminate the limitations with cleaning metal flatware, handling heavy metal cutlery or keeping a large inventory thereof. In addition, it is noteworthy that disposable cutlery offers significant handling advantages compared to its metal-counterparts. For example, a typical cutlery combination containing a fork, a knife, a tablespoon, and a teaspoon would weigh about 200 grams for metal flatware versus about 30 grams for premium plastic cutlery. Applying these weights to a hypothetical 250-person event would yield an overall weight for metal cutlery of about 110 lbs., as compared to only 16 lbs. for plastic cutlery.
Due to the history of terrorist attacks in airplanes and the potential threat resulting from misuse of stainless steel flatware as weapons, there has been an increased tendency for major airline organizations to utilize disposable plastic cutlery while serving meals during flights. However, the use of disposable plastic cutlery affects the image of the airline, especially in premium seating and higher priced flights.
A significant number of upscale catering establishments utilize disposable plastic cups, plates, and bowls etc. for catering functions. However, there is a general preference for continued use of traditional metal cutlery. The primary reason is the less-than-classic appearance, perception and image of plastic cutlery compared to stainless steel flatware. Although stainless steel cutlery is stronger than plastic cutlery, heavy weight plastic cutlery is functionally adequate for most occasions. Thus, a primary obstacle for use of disposable cutlery in such catering events is perception and the image associated with disposable cutlery rather than its performance.
From the foregoing, it can be readily appreciated, that there is a need for cutlery implements that offer the disposability of plastic cutlery and the upscale perception of real stainless steel flatware. Thus, imparting a metallic appearance to disposable plastic cutlery would enhance the perceived value and quality of the cutlery items. A metallic appearance would also lead to greater acceptance of disposable cutlery, as worthy replacements for metal flatware, for use at various events and occasions by caterers and other food-service establishments.
The same is true for the additional tableware items such as cups and plates, although to a lesser extent. Employing a metallic appearance such as gold or silver to the plates and cups to coordinate with the cutlery enhances the aesthetics and provides a more regal presence. The state of the art generally does not introduce metallized cups and plates due to the difficulties discussed herein. Thus while the present description focuses on cutlery, the information is also relevant to other tableware items.
Various methods of imparting a metallic look have been utilized in the prior art. One of the most common and inexpensive methods of imparting a metallic look to plastic parts is the incorporation of a metallic pigment, in the plastic resin, during the molding process. The metallic pigments, typically, have a high metal-content loading. Metallic pigment additives and colorants are manufactured and sold by a variety of pigment and master-batch colorant manufacturers such as Clariant, Engelhard and EM Industries. Other methods commonly employed for enhancing the visual impact of a plastic part and enhancing its commercial appeal consist of applying a finish or graphic to some portion or the entire article. A variety of methods for decorating plastic articles, including printing, hot stamping, heat transfers, in-mold decorating, spray painting, and electroplating are known. Printing techniques have been further classified as silk screen printing, gravure or offset printing, and pad transfer printing (see Hilestad, K., Decorating and Printing, Modern Plastics Encyclopedia 1999, F-7).
It has been the experience of the inventors of the present invention and those skilled in the art that traditional decorating and plastic pigmenting techniques do not impart a commercially acceptable metallic look to plastic cutlery due to a variety of reasons.
First, it is the general experience of those skilled in the art that these metallic pigments do provide a level of sheen to the plastic surface, but do not approach the polished metal look of fine cutlery. In addition, some of the formulations for metallic pigments have an odor which is less-than-desirable for a food-service item.
Second, metallic inks do not approach the genuine look of polished stainless steel flatware.
Third, environmental and food contact issues associated with cutlery further limit the use of metallic inks and carrier solvents that can be used for imparting a metallic look.
Fourth, fine stainless steel flatware is often characterized by an intricate design particularly on the handle of the cutlery items. Consistent with the objective of this invention, namely, to render fine plastic cutlery that is practically indistinguishable from fine metal cutlery requires that design trends be in general agreement with traditional flatware for commercial acceptance. This poses a particular problem with in-mold labeling, wherein a label is strategically placed inside the mold, prior to molding, and hot plastic is introduced into the mold to affect label adhesion on the molded part. The fine and intricate design provided on the surface of the plastic cutlery interferes with label adhesion and results in wrinkling of the label in the areas containing the fine design details.
Fifth, hot stamping, particularly metal foil stamping can provide an authentic metallic-look when strategically placed on a plastic surface. However, hot foil stamping poses the same challenges previously described with in-mold labeling, where foil wrinkling and inconsistent adhesion in the intricate detail areas limit the utility of the foil stamping process for obtaining metallic-look cutlery.
Sixth, electroplating methods are undesirable due to the environmental impact associated with electroplating chemicals as is known in the art.
Various metallizing methods are known, including U.S. Pat. No. 5,022,554 that describes metallized tableware, such as plates, cups, etc., made of a paper substrate, a metallized plastic film joined to the substrate, and an FDA approved top coating over the plastic film. This method of obtaining a metallic-look food service items by laminating a metallized film is not readily applicable to cutlery due to the fact that most plastic cutlery is generally produced by the injection-molding process wherein the feedstock is thermoplastic resin pellets and not laminated film. The shortcomings of incorporating a metallic foil or label during injection molding plastic cutlery have been discussed herein above. Similar shortcomings would apply to the use of a laminated metallic film.
Other approaches to metallization such as those used by Quest et al. (U.S. Pat. Nos. 5,177,124 and 5,280,052) describe a utilitarian and/or decorative object and a method for forming plastic parts having a metallic outer face, appearance and hand. In this technique, a mixture of a liquid monomer, curing agent, a dispersion of metal particles and floatable particles are poured into a mold. The mold is then centrifuged to cause the metal particles to migrate towards the surface of the piece before the monomer polymerizes and hardens to bind the particles. After removal from the mold, the outer face of the piece is polished and buffed to remove the plastic skin from the metal surface, whereby the resultant plastic piece simulates the appearance of a solid metal piece. This method is too cumbersome for application to plastic cutlery as most plastic cutlery is either made of polystyrene and/or polypropylene which are thermoplastic polymeric materials and not monomeric as the above prior art teaching suggests. In addition, the typical process for producing cutlery is injection molding and it is difficult and cost-prohibitive, if not impossible, to rotate a heavy injection mold. And, finally the secondary step of cleaning and buffing the plastic piece is expensive and unacceptable for food-service use.
Various references are available on plating of plastic materials by chemical deposition techniques, electro-deposition techniques and/or a combination thereof. Some plating methods are described in U.S. Pat. Nos. 3,607,350; 3,629,922; 3,896,252; 3,962,494; 4,4,610,895; 3,445,350; 4,039,714; 4,073,743; 4,195,117; 4,810,333 and numerous others. These techniques are essentially wet processes and require that parts be brought into contact with solutions containing metal ions, which must then be washed off to remove any residual chemicals and for general hygiene reasons for a food service article. These processes are relatively unattractive for metallizing cutlery because of the high process and environmental costs.
Thus, it can be readily established that there is a need for fine plastic cutlery that has an enhanced visual and commercial appeal. The improved plastic cutlery should be inexpensive, permitting simple disposal and not requiring separation from food refuse. Such an invention should be manufactured without environmental shortcomings generally associated with metal-plating wet processes. An improved plastic cutlery article should be fabricated primarily from plastic materials, yet have the appearance of genuine metal on the outer surface such that it is practically visually indistinguishable from fine metal cutlery.